The granulomatous lung disorders occur in 20 to 50 Per 100,000 of the U.S.A. population. The "model" disorder of this group is sarcoidosis, a disease characterized by the accumulation of activated helper T-lymphocytes at sites of disease. These T-cells spontaneously express the interleukin-2 gene, thus driving T-cells in the local milieu to proliferate. Evaluation of T-cells in these individuals demonstrates clonal populations, some with partial DJ rearrangements of the beta-chain of the T-cell antigen receptor and others using specific variable regions of the beta-chain. Evaluation of lung T-cells of individuals with chronic beryllium exposure demonstrated that beryllium clearly acts as an antigen, driving proliferation of helper T-cells in this disorder.